Internal combustion engines draw in an air/fuel mixture via an intake channel and additional combustion air via an air channel. The intake channel is opened only over a specific range of a crankshaft revolution. Especially in two-stroke engines, the intake channel is otherwise closed by the piston. A pressure wave occurs in the intake channel because of the periodic opening and closing of the intake channel to the crankcase. The pressure wave is alternately directed toward the crankcase and toward the air filter. The pressure wave can propagate up to the air filter and can tear fuel droplets from the intake channel along into the air filter. In this way, fuel droplets from the air filter can also reach the air channel.
It is known from U.S. Pat. No. 5,582,146 to mount a baffle pot on the air filter in the direction toward the intake channel. This baffle pot is intended to catch fuel droplets thrown back from the intake channel. The fuel collected there is to be carried by the air flow back into the intake channel. A baffle pot of this kind, however, partially covers the opening of the intake channel so that the intake resistance increases. The baffle pot defines an additional component which increases the complexity in production, assembly and storage.
It is known from U.S. Pat. No. 6,415,750 that air channel and intake channel open into separate chambers on the clean side of the air filter. Different pressures can be present in the chambers whereby the mixing ratio of fuel and air changes and the combustion can be hindered.
It is known from U.S. Pat. No. 5,503,649 to mount two rows of air resistance elements between the intake opening and the housing interior space on which fuel and oil should deposit. The rows of air resistance elements lie at a spacing to each other and lead likewise to different pressures at the intake channel and at the air channel.